1. Field of the Invention
This invention relates to a linear guide device in which a carriage slides on a long rail, and in particular to improvements in a ball circulation path in a miniature linear guide device.
2. Description of the Prior Art
Among linear guide apparatus using a rolling guide, there is known one device which comprises a long rail, a carriage of saddle-like shape (C-shaped cross-section) comprising a body and end caps, and a number of balls for permitting the carriage to slide on the rail. The rail of this linear guide is formed with grooves in the opposite side surfaces thereof parallel to the center axis (lengthwise direction) of the rail, and the body of the carriage is formed with grooves opposed to said grooves. The set of grooves are proximate and opposed to each other, whereby a passageway for the balls is formed. A through-hole having a diameter slightly greater than the diameter of the balls and functioning as a ball return passage is formed in the body of the carriage in juxtaposed relationship with said passageway, and said through-hole and said passageway are connected together by a set of semidoughnut-shaped curved passageways further formed in the end caps, whereby a closed circulation path in which the balls may circulate is formed and the carriage is lightly slidable axially on the rail through the rolling of the balls.
In manufacturing the linear guide device, said through-hole is formed by a drill, but the through-hole is a deep hole and therefore, the formation thereof requires a number of working steps. Particularly, in a miniature linear guide device, the number of working steps is so great that it forms a bottleneck manufacturing. The reason is that the diameter of the through hole is as small as 1-3 mm, whereas the length of the through-hole is as great as 20-50 mm and therefore the working efficiency is low and a long working time is required. Also, the drill is often damaged and further, the through-hole tends to bend. When the through-hole bends, a level difference is created in the ball circulation path to cause unsatisfactory circulation of the balls, which often means the production of defective products.